What is the difference between Phd Accounting and Finance?

I really don't have a clue about the differences between accounting and finance. I guess they either interested in researching different questions, or using different methods to approach problems (or both).

I guess that studying at a certain department will expose you to more problems and methods and research relevant to that area - so yes - once you have your phd you can research anything you like, but it is likely that after spending 4-5 years focusing on one aspect it would be easier and more likely that you stay there. inside the program, there might be cross references between the two - but basically you'll have to find advisor within the department - so your PhD research should fall in the boundaries of interests of people within your chosen department.

if you are putting too much emphasis on future pay - you are probably go in the wrong direction and academia might not be for you (especially in acct/fnce - you can get higher pay in the industry with very little effort, and you don't have to work hard for 4-5 years before start being paid).

hope this naswers some of your questioins